Children across the United States are insufficiently physically active. In response, numerous physical activity (PA) interventions have been developed and tested, the majority within the school setting. Unfortunately, these have resulted in limited, if any impact on children's PA. We feel that this absence of effect stems from a lack o tailoring at the school level and a resulting lack in institutionalization. To address the latter isue, we feel that it is important to leverage existing resources and capitalize on existing policies. Th state of South Carolina has instituted the role of Physical Activity Coordinators to promote PA among students across and beyond the school day. However, while these positions are mandated by state law, the individuals in these positions often lack the training and support to maximize their impact. Our long-term goal is to develop best practices to inform the national movement to train school PA Coordinators to deliver a Comprehensive School Physical Activity Program (CSPAP) within schools that can be disseminated across the country. The objectives of the current application are to: 1) modify and expand existing CSPAP training curricula for PA Coordinators; 2) deliver the enhanced PA Coordinator training in our pilot schools; 3) conduct process evaluation on the implementation of a CSPAP by the PA Coordinators, and 4) evaluate the effectiveness of the trainings to increase children's objectively measured PA. The goal of the proposed study is to determine the acceptability, feasibility, and effectiveness of properly traine PA Coordinators to promote PA in elementary school children. This goal will be achieved through the following aims: AIM 1: Develop an enhanced CSPAP training course and resource toolkit for PA Coordinators. AIM 2: Determine the acceptability/feasibility of the enhanced PA coordinator training and the implementation of a Comprehensive School Physical Activity Program in an elementary school setting. AIM 3: Determine the effectiveness of trained PA coordinators to increase objectively measured PA in elementary school youth. We will randomize four schools to receive the PA Coordinator training (n=2) or continue standard practice (n=2). A comprehensive process and impact evaluation will be conducted to determine acceptability of the intervention, factors influencing implementation fidelity/dose, and the effectiveness of the PA Coordinators to increase physical activity measured via accelerometry in children.